Besides Menu.com.do, El periodico El Caribe has good restaurant information:
http://www.elcaribe.com.do/restaurantes.aspx
Also, every Thursday I think they still publish their Guide on City Life, the Bureo Magazine which is really good. The online version is alright but they do not include all the details, so you need to buy the magazine and they have not updated the Bureo website in weeks.
They always include a huge section on restaurants and information on new openings.